And headphone use may be different because the sound source is only millimeters away from the ear drum, with the external auditory canal being even shorter in children than in adults.

Personally, I would advise against the use of headphones and ear buds, period. If you insist on using them keep in mind that if you can’t hear ambient noise when listening to content or music using headphones or earbuds, the volume is too high and is almost certainly causing hearing loss.